Wednesday 1 April 2015

A Versatile 630m Antenna

Mark, VA7MM, had come up with a nicely-designed antenna that will serve as his main 630m radiator. Not only that but it can be used on 10m, 15m and 30m and 160m as well!

The antenna consists of a mini-flat top dipole, with three resonant dipole legs all terminating at a common feedpoint.

This can be used directly on any of the three high bands. Shorting the end of the coaxial cable, dropping vertically down from the feeedpoint, the dipole feedline becomes the vertical element of a top-loaded 630m 'T' antenna, 100' in the air.

With suitable loading coils and appropriate switching, the 'T' will also be used on 160m, making the versatile antenna work on five different bands ... a nice demonstration of basic antenna principles put into real practice!


Unknown said...

I like your antenna but would like to also build one could you give dimensions that you have come to to make it work N9IWW

Steve McDonald said...

Kevin - the antenna is the one built by VA7MM. It is essentially three dipoles (10m, 15m and 30m) all fed from one coaxial feedline. For these three bands, the antennas each work as individual dipoles. One 160m and on 630m, the feedlines is shorted at the end and it is fed as a top-loaded vertical. Enough inductance is connected in series at the base, to resonate the antenna on either 160 or 630m, depending on which coil is switched in. For these two bands, a system of ground radials is also required.


Unknown said...

Isn't a Fan Dipole the same thing? I have made them and stacked the wires
from 6 thru 160 being on the top. All fed from one feed line.

Steve McDonald said...

Yes it is but this one is rather unique in that the normal 'fan' has been configured in a wide horizontal plane and then used as the top-hat for a base-loaded 630m (~475kHz)vertical...which works very well.